Defrosting device for refrigeration apparatus



Nov @Qww s, MCCLOY mm mz DEFROSTING DEVICE FOR REFRIGERATION APIARATUS Filed June 4, 1946 2 Sheets-Sheet l Flank,

BNVENTOR WITNESSES:

GRAMM $.MQQLOY G. S. M CLOY Nov. 8, 1949 DEFROSTING DEVICE FOR REF RIGERATION APPARATUS 2 MiJd 5 R c M 6 MM 7.

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.r m m n m M Y B e E M M ATTORNEY Patented Nov. 8, 1949 DEFROSTING DEVICE FOR REFRIGERATION APPARATUS I Graham S. McCloy, Springfield, Mass., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 4, 1946, Serial No. 674,269

7 Claims.

This invention relates to refrigeration apparatus and more especially to a means for defrosting an evaporator of such apparatus.

It is an object of this invention to provide a novel means for rapidly defrosting a refrigerant evaporator.

It is a further object of the invention to provide a circuit in which a warm refrigerant may be circulated to defrost the evaporator which forms a part of the circuit.

It is another object of the invention to provide an electric defrosting device for a refrigerator in which device the electric shock hazard is reduced.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawings forming a part of this application, in which:

Fig. 1 is a view in perspective of a domestic refrigerator having a frozen food storage compartment in the lower portion of the food cabinet and a general refrigerated food storage compartment in the upper portion thereof; and

Fig. 2 is a schematic drawing of the refrigerating and defrosting mechanism of this invention.

Referring to the drawings, the reference numeral l designates a refrigerator cabinet having a food storage compartment l2 and a machine compartment H in which the refrigerating mechanism i8 is housed. The food storage compartment I2 is divided by a partition l8 into an upper compartment 20 for food storage at above-freezing temperature and a lower compartment 22 for the storage of frozen foods.

The lower compartment 22 is refrigerated through a series type conduit 24, which includes a convoluted evaporative portion 28 and is secured to the inner wall surface of the inner shell 28 of the compartment 22. The conduit 24 includes an inlet tube 30 and an outlet tube 3!, both of which are located in the thermal insulation 32 of the rear wall 34 of the food storage compartment I2. The inlet tube 30 is supplied with liquid refrigerant through a capillary tube 38 from a condenser 38. The condenser 38 receives compressed refrigerant vapor from a compressor 48 located in a sealed casing 42. An electric motor (not shown) for driving the compressor 40 is also located in the sealed casing 42 and is supplied with electrical energy through leads 54 and B. Included in one of the leads 54 is one side of a double-throw switch 58.

The inlet 44 of the compressor 40 communicates with the interior of the casing 42, which, in turn, communicates through a suction tube 48 with a refrigerant header 48 located in an upper portion of the rear wall 34 of the food storage compartment l2. The refrigerant header 48 connects with the upper end of the outlet tube 3| of the conduit 24.

The above-described mechanism forms a primary refrigerating system which directly cools only the lower compartment 22 of the food storage compartment l2. The upper compartment is cooled by a secondary refrigerating system which comprises an evaporator coil 50 located on the outer wall surface of the inner shell 28 and a secondary condenser 52 located in the refrigerant header 48.

The apparatus more directly related to the defrosting mechanism of this invention comprises a chamber located ll\ the thermal insulation 32 of the rear wall 34 of the cabinet 10, and at about the level of the lower part of the evaporative portion 26. An electric heating element 62 is located within the chamber 60 and is energized through leads 64 from the leads 56. Included in one of the leads 64 is the other side of the doublethrow switch 58.

The upper portion of the chamber 80 communicates with the conduit 24 just prior to the evaporative portion 26 thereof. A duct 66 communicates with an upper portion of the conduit 24 and with a lower portion of the chamber 66. The duct 66 is embedded in the thermal insulation 32 of the rear wall of the food storage compartment l2 and is in heat transfer relationship with the inlet tube 36 of the conduit 24. The duct 65 is of a smooth interior to facilitate the superheating of the refrigerant liquid therein.

()peration Refrigeration of the food storage compartment I2 is effected when the double-throw switch 58 energizes the leads 54 to actuate the compressor 40. Refrigerant vapor is then withdrawn from the refrigerant header 48, is compressed by the compressor 40, and then condensed to a liquid in the condenser 38. The capillary tube 36 carries the refrigerant liquid to the upper portion of the inlet tube 30 from which it flows into the chamber 60 and into the conduit portion 26 wherein it absorbs heat and partly vaporizes. A mixture of refrigerant liquid and vapor passes up the outlet tube 3| of the conduit 24 to the refrigerant header 48 where the remaining refrigerant liquid vaporizes to cool the secondary condenser 52. The condensed refrigerant in the condenser 52 flows downwardly into the evaporator coil 50 to vaporize therein and absorb heat from the upper compartment 20.

During this operation, a column of quiescent refrigerant liquid will form in the duct 66 to a height of about the line 68. The liquid in the duct 66 will not vaporize because of the thermal insulation 32 surrounding it, because of the cooling effect of the inlet tube 30, and because of the smooth interior of the duct 66 which promotes superheating of the liquid column therein. The column of refrigerant liquid in the duct 66 will exceed the weight of the column of mixed refrigerant liquid and vapor in the evaporator portion 26 and in the portion3i of the conduit 24 which joins the evaporative portion 26 with the upper end of the duct 66. Consequently, the refrigerant will flow through the portions 26 and 3| in preference to the duct 66.

When the evaporative portion 26 is to be defrosted, switch 58 is moved to deenergize the leads 54 and energize the leads 64. This stops the compressor and energizes the heater 62 to vaporize some of the refrigerant liquid in the chamber 60. The vapor thus formed cannot escape through the inlet tube 36 because its flow is retarded by the capillary tube 36 and is stopped eventually by the valve mechanism of the compressor 40. The vapor, therefore, fiows into the lower part of the evaporative portion 26, wherein a part of the vapor condenses and melts some of the frost on the evaporative portion 26 by its latent heat of condensation. The remainder of the refrigerant vapor passes upwardly through the evaporator '26, through the outlet tube 3|,

through the header 48, and into the compressor shell 42. The vapor flowing upwardly in the upper portion of the evaporative portion 26 and in the outlet tube 3| acts as a vapor lift pump to lift some of the refrigerant liquid from the evaporative portion 26. This liquid then flows downwardly through the duct 66 to the lower part of the chamber 60, thus establishing a circuit of refrigerant which flows upwardly through the chamber 60, through the evaporative portion 26, upwardly through the outlet tube 3| and downwardly through the duct 66 to the chamber 60. The refrigerant liquid thus circulated is warmed by the heater 62 and will rapidly thaw any frost which remains on the evaporative portion 26.

The thawing of the evaporative portion 26 is so rapid that the frozen food stored in the lower compartment 22 may remain in place during the defrosting operation. It is desirable for uniform and quick defrosting that the evaporative portion 26 comprise a narrow series tube in which the vapor and liquid are carried along together. The series tube 26, however, may be replaced by a flooded evaporator in case a uniform defrosting of all the evaporator passages is not imperative. It will be apparent from the above that this invention provides a rapid means of defrosting an evaporator in which the refrigerant itself is used to effect the defrosting. The invention also provides an electric defrosting device which is buried in the thermal insulation of the cabinet wall to protect the user of the refrigerator from electrical shock. The invention further provides that the refrigeration losses in the tube of the defrosting device are minimized.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof.

What I claim is: I

1. In refrigerating apparatus including a cable net having therma -insu lated walls, a cooling unit adapted to coolthe interior of sa. cabinet, said cooling unit having a refrigerant passage, means adapted to be rendered active and inactive for supplying a volatile refrigerant liquid to and for withdrawing the vaporized refrigerant from said refrigerant passage, the combination with said apparatus of a duct connecting'two spacedtion of the refrigerant passage of said cooling unit, an electric heater located in the thermal insulation of a wall of said cabinet, said heater being in heat transfer relationship with said duct portion, and means for rendering said heater active and inactive, said duct and heater being adapted to circulate warm refrigerant through said cooling unit to defrost the same when said refrigerant suppying means is inactive.

2. The refrigerating apparatus defined in claim 1 wherein said refrigerant supplying means con prises a tube which conducts refrigerant liquid to said refrigerant passage of the cooling unit, said tube being of sufficiently large internal diameter to maintain the refrigerant liquid therein at substantially the same pressure as the refrigerant in said passage, said tube being located in the thermal insulation of a wall of said cabinet and in heat transfer relationship with said duct.

3. The refrigerating apparatus defined in claim 2 wherein said duct is at least in part so elevated above the upper portion of said cooling unit that the elevated part contains refrigerant vapor.

4. In the refrigerating apparatus defined in claim 3 wherein said duct connects with a refrigerant header, the combination with said header of a secondary volatile refrigerant circuit, said circuit having a condensive portion in heat trans- I8! relationship with said header and an evaporative portion in heat transfer relationship with a portion of the interior of said cabinet, said means for withdrawing refrigerant vapor from said cooling unit being connected with said header.

5. The refrigerating apparatus defined in claim 1 wherein said duct is at least in part so elevated above the upper portion of said cooling unit that the elevated part contains refrigerant vapor.

6. In refrigerating apparatus including a cabinet having thermally insulated walls, a cooling unit adapted to cool the interior of said'cabinet, said cooling unit having a refrigerant passage, means adapted to be rendered active and inactive for supplying a volatile refrigerant liquid to and for withdrawing the vaporized refrigerant from said refrigerant passage, the combination with said apparatus of a duct connecting two spacedapart portions of said refrigerant passage, a portion of said duct being at an elevation below at least a portion of the refrigerant passage of said cooling unit, an electric heater in heat-transfer relationship with said duct portion, and means for rendering said heater active and inactive, said duct and heater being adapted to circulate warm refrigerant through said cooling unit to defrost the same when the refrigerant supply means is inactive, said refrigerant supplying means comprising a tube which conducts refrigerant liquid to said refrigerant passage of the cooling unit,

ls-said tube being of sufficiently large internal di- 6 meter to maintain the refrigerant liquid therein at substantially the same pressure as the refrig- REFERENCES CITED erant in said passage, said tub being in The following references are of record in the transfer relationship with said duct, and therfile of this patent: ma] heat insulating material around said tube and Said duct 6 UNITED STATES PATENTS '1. The refrigerating apparatus defined in claim Number Name Date 6 wherein said portion of the duct is at an ele 2,008,628 Rufl July 16, 1935 vation below the lowest portion of the refrigerant passage of the cooling unit. 10

GRAHAM S. MCCLOY. 

